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Report Produced: 10/07/2026 04:43 AM

Report Question ID Question Discussion Answer Cancer Site Category Data Item Category Year
20230068

Solid Tumor Rules/Histology--Thyroid: What is the histology code for a diagnosis of poorly differentiated thyroid carcinoma arising in a background of solid papillary thyroid carcinoma? See Discussion.

Patient had a hemithyroidectomy with the final diagnosis above. There does not appear to be an Other Sites H rule or table that addresses this combination of histologies for thyroid primaries.

Code to poorly differentiated thyroid carcinoma, 8337/3.

In this case the tumor is comrpised of two difffernat thyroid histologies: poorly differentiated carcinoma 8337/3 and papillary thyroid carcinoma 8260/3. WHO does not have a code for this combination. Per our endocrine pathology expert, the poorly differentiated carcinoma is the more agressive histology and will determine treatment and progrnosis.

 Thyroid Histology 2023
20051129 Reportability/Behavior--Thyroid: Does the term "invasion" indicate the presence of a malignant tumor? See Discussion. Left thyroid lobectomy showed microfollicular neoplasm with evidence of minimal invasion. Micro portion of path report stated, "The capsular contour is focally distorted by a finger of the microfollicular nodule which appears to penetrate into the adjacent capsular and thyroid tissue."

We recommend that you contact the pathologist for further information. If no further information is available, do not accession this case based on the information provided. There is no definitive statement of malignancy.

If the case was sent to a consultant, there may be another opinion available. If there is information in the record, or the treating physician can be contacted, find out whether the tumor was benign or malignant and whether there was any further treatment.

According to our pathologist consultant, based only on the information above and nothing else, do not report since there is no diagnosis of malignancy.

 Thyroid Behavior 2005
20220038

Solid Tumor Rules/Histology--Thyroid:  What is the histology code for sclerosing mucoepidermoid carcinoma with eosinophilla in the left thyroid and papillary thyroid carcinoma in the right thyroid?  See Discussion.

The left thyroid lobectomy/isthmusectomy returned a diagnosis of sclerosing mucoepidermoid carcinoma with eosinophina, 6.5 cm, replacing nearly the entire left lobe of the thyroid.

The patient has a completion thyroidectomy of the right lobe and returned the diagnosis of papillary thyroid carcinoma, 0.5 mm, in maximum dimension.

The endocrinologist describes it as "co-exsisting" and states the tumor is iodine non-avid.

Abstract two primaries and assign code 8260/3 (papillary adenocarcinoma, NOS) to the right thyroid using Solid Tumor Rules, Other Sites, Rule H14, and 8430/3 (mucoepidermoid carcinoma) to the left thyroid as these are separate tumors with different histology types according to WHO Classification of Tumors of Endocrine Organs, 4th edition.

 Thyroid Histology 2022
20031189 Multiple Primaries (Pre-2007)--Thyroid: Would a papillary carcinoma of the right lobe of the thyroid diagnosed approximately 2 1/2 years after a papillary carcinoma of the left lobe be coded as a second primary? See Description.

8/31/1999: papillary carcinoma, left lobe thyroid, treated with lobectomy.

1/17/2002: papillary carcinoma, right lobe, treated with lobectomy, completion thyroidectomy.

For tumors diagnosed prior to 2007:

Yes, this is a second primary. The second papillary carcinoma was more than 2 months after the first and not specified as recurrent or metastatic.

For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.

 Thyroid N/A 2003
20220017

Histology--Thyroid: What is the correct histology code for a thyroid resection showing papillary carcinoma, tall cell variant with oncocytic features with 30% of largest tumor (right) is tall cell variant and both foci contain benign multinucleated giant cells?  See Discussion.

There is an ICD-O histology code for papillary carcinoma, tall cell (8344/3) as well as papillary carcinoma, oxyphilic cell (8342/3). Per SINQ 20150045, the term oncocytic is synonymous with oxyphilic in this context.

The term “variant” can be used for the Other Sites (non-updated STR sites) primaries when the ICD-O-3.2 (or ICD-O-3 for older cases) includes the term “variant” in the histology name. The MPH General Instructions did not include the term “variant” as a term that can be used to code histology.

Code papillary carcinoma, tall cell variant with oncocytic features to papillary carcinoma, tall cell (C73.9) (8344/3).  The WHO Classification of Endocrine Organs states that this variant is composed of cells that are as tall as they are wide, and show abundant eosinophilic (oncocytic-like) cytoplasm.  Tall cells must account for greater than or equal to 30% of all tumor cells.

 Thyroid Histology 2022
20200087

Solid Tumor Rules (2018)/Histology--Thyroid: What is the correct histology code for a micropapillary thyroid carcinoma for cases diagnosed 1/1/2021 and later? See Discussion.

The 2021 ICD-O-3.2 Update includes papillary microcarcinoma (8341/3) as the preferred term for thyroid primaries (C739). However, there are multiple SINQ entries instructing registrars not to use code 8341/3 for diagnoses of micropapillary carcinoma of the thyroid (including SINQ 20071076, 20081127, 20110027, 20150023, and 20180008).

SINQ 20150023 specifically indicates: Per the WHO Tumors of Endocrine Organs, for thyroid primaries/cancer only, the term micropapillary does not refer to a specific histologic type. It means that the papillary portion of the tumor is minimal or occult (1 cm or less in diameter) and was found incidentally. WHO does not recognize the code 8341 and classifies papillary microcarcinoma of the thyroid as a variant of papillary thyroid carcinoma and codes histology to 8260. If the primary is thyroid and the pathology states papillary microcarcinoma or micropapillary carcinoma, code 8260 is correct.

Does this clarification apply to cases diagnosed 2021 and later? If WHO feels the term micropapillary still does not refer to a specific histologic type for the thyroid, why is 8341/3 listed as a preferred term for this morphology/site combination? For cases 2021 and later, should a diagnosis of Incidental papillary thyroid microcarcinoma (3 mm) in left lower pole, be coded as 8341/3 per the ICD-O-3.2, or as 8260/3 per clarification in multiple SINQ entries?

This question was prompted from preparing SEER*Educate coding exercises. We will use the answer as a reference in the rationales.

Continue to code micropapillary thyroid carcinoma to 8260/3 until instructed otherwise. This coding instruction is based on input from expert endocrine pathologists. This issue will be revisted based on the 4th Ed WHO Endocrine Tumors and updated if needed.

 Thyroid Histology 2020
20091027 MP/H Rules/Multiple primaries--Thyroid: How many primaries should be coded in a patient with a 4/5/08 left thyroid lobectomy diagnosis of follicular carcinoma followed by a 7/25/08 right thyroid lobectomy diagnosis of papillary carcinoma, follicular variant?

For cases diagnosed 2007 or later:

Rule M17 under Other Sites applies. These are separate primaries based on their ICD-O-3 histology codes. Follicular carcinoma is coded 8330. Papillary carcinoma, follicular variant is coded 8340. The histology codes are different at the third number. Rule M6 does not apply because these diagnoses are more than 60 days apart.

 Thyroid N/A 2009
20220018

Solid Tumor Rules/Histology--Thyroid:  What is the correct histology code for the following thyroid primary with multiple tumors abstracted as one primary diagnosed prior to 2021?  See Discussion.

2016 Total thyroidectomy, Multifocal

-Dominant Tumor:  Right Lobe, Papillary thyroid carcinoma (8260/3)

-Tumors two through five:  Three tumors Papillary thyroid carcinoma (8260/3), and one tumor Papillary thyroid carcinoma, follicular variant (8340/3)

-An additional tumor: Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (8343/2)

Code this multifocal thyroid carcinoma, single primary, as papillary thyroid carcinoma, follicular variant (8340/3) using Solid Tumor Rules, Other Sites, Rule H13 that says to code the most specific histologic term. We consulted with our endocrine specialty pathologist and when there is a mix of papillary and follicular variants, assign 8340.

Non-invasive follicular thyroid neoplasm with papillary-like nuclear features is coded as 8349/1 beginning in 2021.  According to the WHO Classification of Endocrine Organs, 4th edition, it was formerly classified as non-invasive encapsulated follicular variant of PTC (FVPTC) (8343/2) but was reclassified based on extremely low malignant potential.

 Thyroid Histology 2022
20230032

Reportability/Histology--Thyroid: Is a diagnosis of papillary carcinoma, follicular variant, encapsulated/well demarcated, non-invasive reportable? See Discussion.

The final diagnosis for a left thyroid lobectomy was Papillary thyroid microcarcinoma, further stated to be Histologic Type: Papillary carcinoma, follicular variant, encapsulated/well demarcated, non-invasive. The diagnosis comment states there is a small follicular pattern papillary microcarcinoma.

Is the designation of “non-invasive” for this papillary follicular tumor equivalent to a non-reportable diagnosis of Non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), 8349/1? Or should this be accessioned as either a reportable in situ (non-invasive) papillary follicular thyroid carcinoma or a papillary microcarcinoma per the diagnosis comment?

Your case is equivalent to encapsulated follicular variant of papillary thyroid carcinoma, non-invasive (non-invasive EFVPTC) and is not reportable for cases diagnosed in 2021 or later even though it says "carcinoma." That is because the WHO assigned a behavior code of /1 to this entity (8349/1). NIFTP is assigned to the same histology and behavior code.

 Thyroid Histology 2023
20170065

MP/H Rules/Histology--Thyroid: How should histology be coded for a single tumor with final diagnosis undifferentiated (anaplastic) carcinoma arising in association with papillary thyroid carcinoma and the Summary Cancer Data states Histologic type: Undifferentiated (anaplastic) carcinoma only? See Discussion.

The Summary Cancer Data does not seem to describe a more specific histology, but it does describe the tumor histology with the worst outcome and the most extensive tumor. The anaplastic carcinoma grossly extended into skeletal muscle and gave rise to multiple regional lymph node metastases. The more appropriate histology seems to be 8021.

However, current MP/H Rules for a single tumor indicate the histology should be coded to the numerically higher histology code (8260). Coding the histology to 8260 does not account for the more aggressive tumor. Should this histology be 8260 or 8021?

Code the most specific histologic term, 8260, for papillary carcinoma of the thyroid using Multiple Primary/Histology Rule H13 for Other Sites (single tumor, invasive section). Use text fields to describe the complete histology.

 Thyroid Histology 2017